Small electric car charging in public parking lot.
March 2, 2016

Scientists develop carbon-negative electric car battery production technique

A team of scientists from Vanderbilt University and George Washington University may have just figured out a way to bite out of the global carbon crisis, but it’s not the way you might think—because it involves driving cars.

Well, sort of, as the team has managed to create electric car batteries that are carbon negative—meaning, their manufacturing process uses up atmospheric carbon.

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Running a carbon-negative world

As described in ACS Central Science, the team adapted a process that made its debut in August in Nano Letters. Known as a solar thermal electrochemical process (STEP), it effectively splits carbon dioxide, producing carbon and oxygen gas. The carbon is then turned into nanotubes, which are not only conductive, but stable, flexible, and stronger than steel.

“This approach not only produces better batteries but it also establishes a value for carbon dioxide recovered from the atmosphere that is associated with the end-user battery cost unlike most efforts to reuse CO2 that are aimed at low-valued fuels, like methanol, that cannot justify the cost required to produce them,” said Assistant Professor of Mechanical Engineering Cary Pint, of Vanderbilt University, in a statement.

Even better, though, the STEP process to make the batteries is solar-powered: Sunshine provides both the heat and electricity necessary to break down the CO2.

Credit: Julie Turner / Vanderbilt University

Credit: Julie Turner / Vanderbilt University

“Our climate-change solution is twofold: (1) to transform the greenhouse gas carbon dioxide into valuable products and (2) to provide greenhouse gas emission-free alternatives to today’s industrial and transportation fossil fuel processes,” said Professor of Chemistry Stuart Licht, of George Washington University.

The benefits of carbon nanotubes

“In addition to better batteries other applications for the carbon nanotubes include carbon composites for strong, lightweight construction materials, sports equipment and car, truck and airplane bodies.”

In particular, these nanotubes can be used in both lithium-ion batteries (commonly found in electric vehicles and iPhones) and sodium-ion batteries, which are currently sold as backup power supplies for electricity grids. The nanotubes replace the carbon anode used in commercial lithium-ion batteries; for sodium-ion batteries, nanotubes replace graphite electrodes.

For the lithium-ion batteries, the carbon nanotubes provide a small boost to performance—which increases when the batteries are charged quickly. When they added small defects in the carbon of sodium-ion batteries, meanwhile, the researchers discovered that the nanotubes lead to a more than 3.5 times better battery storage performance over the traditional sodium-ion option.

But perhaps most importantly, both kinds of carbon-nanotube batteries held up over the course of 2.5 months of continuous charging and discharging, showing no signs of fatigue.

Currently, Pint estimates that recycled carbon dioxide could compose around 40 percent of a battery, not including the packaging—which could likely be made out of a similar STEP process in the future, using up more carbon dioxide in the process.

“Imagine a world where every new electric vehicle or grid-scale battery installation would not only enable us to overcome the environmental sins of our past, but also provide a step toward a sustainable future for our children,” said Pint. “Our efforts have shown a path to achieve such a future.”

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Image credit: Vanderbilt University/Cary Pint